Manual control system for numerically controlled machine

ABSTRACT

A manual control system including a powered feed for a numerically controlled machine tool. The system includes a manually operable differential resolver located in the position feedback loop of the servo control system for each slide and a variable speed motor for driving that differential resolver at a controlled rate so as to effect controlled feeding movement of the slides independent of the numerical control unit.

United States Patent 1191 [111 3,766,466 Hentz et al. Oct. 16, 1973MANUAL CONTROL SYSTEM FOR 2,750,545 6/1956 Davis 318/661 NUMERICALLYCONTROLLED MACHINE 3,156,438 11/1964 Diller et al.... 3181628 X u I3,173,001 4/1965 Evans 235/154 [75] Inventors: Thomas E- Hentz, Cmcmnatu3,576,535 4/1971 Turner 318/591 x Robert K. Burroughs, Batavia, both3,686,556 8/1922 Anger 318/605 X of Ohio [73] Assignee: LeBlond Inc.,Cinicinnati, Ohio 'y Examiner-B- Dobeck Filed y 3 1972 I Attorney-JamesS. Hight et al.

9 [2]] Appl. No.: 250,076 [57] ABSTRACT [52] Cl 318/571 3 18/39 318,605A manual control system including a powered feed for 318/661 anumerically controlled machine tool. The system in- 51 Int. (:1. G05b11/18 cludes a manually differential 58 Field of Search 318/628 571' 575cated in feedbad 318,590 591 605 6 trol system for each slide and avariable speed motor for driving that differential resolver at acontrolled [56] Referencescited rate so as to effect controlled feedingmovement of the slides independent of the numerical control unit.

UNITED STATES PATENTS 2,475,484 7/1949 Nise 318/628 28 Claims, 2 DrawingFigures 1 MANUAL CONTROL SYSTEM FOR NUMERICALLY CONTROLLED MACHINE Thisinvention relates to automatically controlled equipment and particularlyto numerically controlled machine tools.

Numerically controlled machines are controlled from a program, usuallyin the form of a tape or a programmed card. In addition to theprogrammed source of machine control, most numerical controlled machinesalso have a manual data input through which programmed information maybe supplied to the machine for single cycle operation or for machinesetup. However, the input of data through the manual data input requiresthat the information be supplied to the machine through the numericalcontrol unit and that in turn requires that the person putting the datainto the control unit be a programmer. In other words, the machineoperator who desires to cycle the machine through a single cycle withoutprogramming a tape or card must supply the manual data input to thecontrol unit in the same form and in the same sequence as it is suppliedto the unit by the tape and consequently that operator must have all theskills of a machine programmer. Unfortunately, most machine operators donot have a programming skill and therefore cannot operate numericallycontrolled machines except through a programmed drive. But there isoften a need for a numerical control machine to be operated through asingle cycle, as for example, to machine soft jaws of a chuck duringsetup of a machine preparatory to cycling of the machine under thecontrol of a programmed tape or card. v

At the present time many numerically controlled machines have, inaddition to the manual data input control, some manually operatedmechanism for positioning a slide of the machine during machine setup.Quite often this manual positioning comprises a dial operateddifferential resolver in the positioning feedback loop of the slidecontrol servo system. When the dial is manually rotated, it effectscorresponding displacement of the slide. However, that manual rotationof the graduated dial effects slide movement at very nearly exactly thesame rate as the dial is rotated. Consequently, it is impractical to useit to control slide movement velocity or in the case of a machine tool,to control machine feed rates. Therefore, even machines which areequipped with auxiliary positioning input independently of theprogrammed control unit still require manual data input at the controlunit whenever the machine is to-be cycled through a single machiningcycle or whenever the slide is to be moved at a controlled speed.

. It has therefore been one objective of this invention to provide amanual control of a machine slide on a nu merically controlled machinewhich controls not only positioning but rate of movement or feedcompletely independently of the control unit. Expressed another way,ithas been an objective of this invention to provide a control systemfor a numerically controlled machine which enables an operator to'effectslide movement at a feed rate or velocity selectable by the operatorusing a calibrated manual control knob at the machine. This enables themachine operator to operate the machine in the exact same manner as ifthemachine had no numerical control unit. Consequently, any operator whoknows absolutely nothing about machine programming but who has learnedhow to operate a similar machine manually is able to operate anumerically controlled machine equipped with the invention of thisapplication.

The system which accomplishes these objectives comprises a manuallyoperable differential resolver located in the position feedback loop ofthe machine servo control system and a variable speed motor for drivingthat differential resolver. In the preferred embodiment the variablespeed motor is located in a servo loop which includes a tachometer and amanually operable speed control potentiometer so that the rate at whichthe variable speed motor drives the differential resolver may be veryaccurately controlled.

The primary advantage of this invention is that it provides a veryinexpensive manually operable feed rate control for a machine tool slideof a numerically controlled machine. The addition of this inexpensivemanual feed rate control enables any operator capable of operating asimilar machine without numerical controls to operate this numericallycontrolled machine. Consequently, a numerically controlled machine withthis manual position and feed rate control is useful as both a manualcontrolled machine and as a numerically controlled machine and may beeasily and quickly switched between such uses.

These and other objects and advantages of this invention will be morereadily apparent from the following description of the drawings inwhich:

FIG. 1 is a perspective view of a lathe incorporating the invention ofthis application; and

FIG. 2 is a block diagram of the electrical control system for the latheof FIG. 1.

Referring first to FIG. 1, there is shown a typical machine 10 of thetype to which the invention of this application is applicable. In thepreferred embodiment, the machine is a lathe although the invention ofthis application is applicable to any programmable machine but isparticularly adaptable to metal cutting or forming machines. The lathe10 includes a headstock 11 having a chuck (not shown) attached to theheadstock spindle for holding and rotating a workpiece. The lathefurther includes a longitudinally movable carriage 12 which supports andcarries a slide 13 movable toward and away from a workpiece. The slide13 in turn carries a tool which follows the longitudinal movements ofthe carriage 12 and the transverse movements of the slide 13, thesedirections being designated as the Z and X directions respectively.Motion along the Z axis is typically provided by rotation of a carriagelead screw 14 (FIG. 2) while motion along the X axis is typicallyprovided by rotating a cross feed screw 15 (FIG. 2). The lead screw 14is driven by a feed motor 16 while the cross feed screw 15 is driven bya second feed motor 17.

Referring now to FIG. 2 and the block diagram of the control system usedto control the lathe 10, it will be seen that the lathe control systemhas been divided into two sections 44, 45, one for the control of eachof the X and Z axes. Since the two controls are identical, only one(that which controls the X axis) will be described in detail exceptwhere a discussion of the equipment of both coordinates is required forclarification. For purposes of identification the control equipment forthe Z axis has been given the same numerical designation as thecorresponding equipment for the X axis except that the Z axis controlequipment is designated by a numeral followed by a prime mark.

Essentially, the X axis motor control system 44 includes a servo loopfor controlling both the position and velocity of screw 15 rotation. Acommand signal for controlling both position and velocity is derivedfrom the numerical control unit 20. Suitable control units arecommercially available for operation in this circuit. One such suitablecontrol circuit is described in U.S. Pat. No. 3,173,001 issued Mar. 9,1965 to J.T. Evans. That command signal is supplied to a positionsumming point or comparator 21 out of which an error signalE is suppliedto a position amplifier 22 on lead 23. The output of that amplifier 22is then supplied through a velocity summing point or velocity comparator24 and a velocity amplifier 25 to the main servo feed motor 17. The feedmotor 17 is mechanically connected to an electrical resolver 26 and atachometer 27. The resolver 26 is connected in a primary feedback loopvia lead 28 to the summing point comparator 21 such that the errorsignal on lead 23 represents the difference between the commandreference signal C on lead 29 and the primary feedback signal on lead28. The tachometer 27 also gives rise to a feedback signal on lead-30 tothe-summing comparator 24 of the velocity loop so that the velocitysignal out of the comparator 24 represents the difference between theactual motor speed and .'the commanded motor speed. Both the velocityand position servo loop are conventional in motor control circuits andboth are described in the above-identified issued patent.

The invention of this application is concerned with a supplementedcontrol system for enabling the servo feed motor 17 to be manuallycontrolled from position control dials 31, 31', a velocity control dial39, and switching controls 18 on the the apron 19-of the machinecompletely independently of the numerical control unit 20. To this end adifferential resolver 32 is connected between the resolver power supply33 and the resolver 26. The rotor of this differential resolver 32 ismechanically connected to the position control dial 31 on the apron 19of the lathesuch that rotation of the dial effects rotation of the rotorof the differential resolver 32 and thereby effects an auxiliary inputon lead 32a to'the resolver 26 and subsequently to the summing pointor'comparator 21 0f the position control loop; Consequently, manualrotation of the graduated positioncontrol dial 31 may be used to effectdisplacement of the servo feed motor 17 and corresponding linearmovement of the 'slide 13. Generally, this graduated-dial 31 is used inmachine setup to position the slide 13 in some zero position preparatoryto the initiation of a numerically controlled machine cycle. This manualinput to the machine by the dial 31 is suitable for positioning theslide preparatory to a cutting operation but is unsuitable for operationwhen cutting because the rate of dial rotation determines the speed orslide movement. It is very nearly impossible to manually rotate thegraduated dial 31 at a rate which is suitable for-feeding a cuttingtoolinto a workpiece.

To control the speed of slide movement and thereby I enable the manualcontrols on the-apron 19 of themachine to be used for controlling bothfeed rate (speed) and position, a variable speed drive motor 34' isdrivingly connected to the differential resolver 32 and the machanicallyconnected graduated dial 31. This motor is operable to drive'the rotorof the differential resolver 32 and thereby effect slide movement at apreselected speed. To accurately control the speed of the drive thesetting of which is controlled by a control'dial 39 located on the apron19 of the machine. The comparamotor 34, it is connected in a servo loopwhich includes a tachometer 35 and a comparator 36 together with a speedpotentiometer 37. The tachometer 35 is mechanically connected to thedrive shaft of the drive motor 34 and is operable to supply a feedbacksignal via lead 38, through a 4-way switch 43 and lead 46 tothecomparator 36. A command signal is suppled to this comparator 36 fromthe speed control potentiometer 37,

tor 36 supplies an output error signal on lead 40 to a velocityamplifier 41, the output of which then is used to drive either the motor34 or motor 34, depending upon the setting of the toggle switch 43, at arate set into the graduated dial 39. The speed control potenti- 'ometerdial 39 may be either graduated in terms of inches per minute or inchesper revolution of the tool spindle, dependent upon the application ofthe system.

In addition to the position control dials 31, 31' and the feed (speed)control dial 39 on the apron of the machine, there is a selector switch42 for selecting either manual or programmed automatic control and -a 4-position axis and direction control joy stick" type of 4-way toggleswitch 43. The switch 42has the effect of holding or freezing thecommand signal Con line 29 so that the only active position commandsignal is that derived from the differential resolver 32. The 4-way joystick switch 43 enables the axis, X or Z, to be s'elected at the apronas well as the direction in which the slide will move along that axiswhen under the control of the speed setting dial 39. i

The use of the drive motor 34 for effecting of the rotor of thedifferential resolver 32 and the location of the speed and positionsetting controls on the apron 19 of the machine enableithe machine to beop erated in exactly the same manner as lathes or other machine toolsare operated which do not incorporate numerical control. Consequently,the auxiliary manual control of this invention enables the machineoperator to interrupt the numerical control unit 20, place the machinein manual control mode, selectthe axis and direction of slide movementvia the 4-way switch43 I and operate the machine in exactly the same wayas similar nonnumerically controlled machines have 'always beencontrolled. Consequently, an old machine operator, no matter howresistant to change, can now operate this numerically controlled machinewithout knowing a single thing about machine programming.

The primary' advantage of this invention is that it enables a lathe ormachine tool to be used in either manual mode of operation or innumerical mode of control. Consequently, the single machine functionsboth as a conventional machine for machining single workpieces or anumerically controlled machine for machining parts in accordance with aprogram schedule. j

While I have describedonly a single preferred em bodiment of myinvention, those persons skilled in the art to which this inventionpertains will appreciate numerous changes and modifications which may bemade without departing from the spirit of my invention. Therefore, I donot intend to be limited except by the scope of the appended claims. 7

Having described my' invention, I claim:

1. For use in combination with a numerically programmable machine havinga slide and a motor for effecting movement of said slide, a controlsystem for rotation controlling energization of said motor, said controlsystem comprising a first source of programmable position and velocitycommand signals,

a comparator,

means for supplying a programmed command signal from said first sourceof command signals to said comparator,

means for supplying an error signal from said comparator to said motor,

a feedback signal generator,

means for supplying a feedback signal from said feedback signalgenerator to said comparator such that said error signal isrepresentative of the difference between said command signal and saidfeedback signal,

a second source of unprogrammed position control signals,

means for supplying position control signals from said second source tosaid comparator, and

the improvement which comprises variable speed motor means for drivingsaid second source of position control signals at a controlled rate soas to control the velocity of slide movement when said slide is underthe control of said second source of unprogrammed position controlsignals.

2. For use in combination with a numerically programmable machine havinga slide and a motor for ef fecting movement of said slide, a controlsystem for controlling energization of said motor, said control systemcomprising a first source of programmed position and velocity commandsignals, a comparator, means for supplying a command signal from a saidfirst source of command signals to said comparator, means for supplyingan error signal from said comparator to said motor, a feedback signalgenerator, means for supplying a feedback signal from said feedbacksignal generator to said comparator such that said error signal isrepresentative of the difference between said command signal and saidfeedback signal, a second manually actuated source of unprogrammedposition control signals, means for supplying position control signalsfrom said second source'to said comparator, and the improvement whichcomprises variable speed motor means for driving said second source ofunprogrammed position control signals at a controlled rate so as tocontrol the velocity of slide movement when said slide is under thecontrol of said second source of position control signals. 3. For use incombination'with a numerically programmable machine having a slide and amotor for effecting movement of said slide, a control system forcontrolling energization of said motor, said control system comprising afirst source of programmed position command signals,

a comparator, means for supplying a command signal from a said firstsource of command signals to said comparator,

means for supplying an error signal from said comparator to said motor,

a resolver for generating a feedback signal,

means for supplying said feedback signal from said resolver to saidcomparator such that said error signal is representative of thedifference between said command signal and said feedback signal,

a manually setable differential resolver for generating unprogrammedcontrol signals, means for supplying said unprogrammed control signalsfrom said differential resolver to said comparator, and the improvementwhich comprises variable speed motor means for driving said differentialresolver at a controlled rate so as to control the velocity of slidemovement when said slide is under the control of unprogrammed controlsignals.

4. The control system of claim 3 in which said differential resolver iselectrically connected in a feedback loop between said resolver and saidcomparator.

5. The control system of claim 3 in which said differential resolvercomprises a stator and a rotor, said rotor being mechanically connectedto a manually rotatable position control dial.

6. The control system of claim 3 in which said variable speed motor isconnected to a manually setable speed control setting means.

7. The control system of claim 3 in which said variable speed motor isconnected through a closed servo loop with a manually setable speedcontrol setting means.

8. The control system of claim 7 in which said closed servo loopincludes a tachometer mechanically connected to said variable speedmotor, a source of command speed control signals, and a comparator forgenerating an error signal representative of the difference between thecommand speed control signal and the actual speed of said variable speedmotor as measured at said tachometer. 1

9. For use in combination with a numerically controlled machine toolhaving a pair of slides movable along mutually perpendicular axes and apair of independently operable motors for effecting movement of saidslides, a numerical control system for controlling energization of saidmotors, said control system comprising I a first source of programmableposition and velocity command signals for each of said motors,

a pair of comparators, one of said comparators being in a controlcircuit for each of said motors, means in each of said circuits forsupplying a programmed command signal from said first source of commandsignals to each of said comparators, means in each of said circuits forsupplying an error signal from said comparator to the motor controlledby said circuit, a feedback signal generator in each of said controlcircuits, means in each of said circuits for supplying a feedback signalfrom said feedback signal generator to said comparator such that saiderror signal is representative of the difference between said commandsignal and said feedback signal, a second source of unprogrammed signalsin each of said circuits,

means in each of said circuits for supplying position control signalsfrom said second source to the comparator in said circuit, and

position control the improvement which comprises variable speed motormeans in each of said circuits for driving said second source ofposition control signals at a controlled rate so as to control thevelocity of slide movement when that slide is under the control of saidsecond source of unprogrammed position control signals.

10. The control circuit of claim 9 in which said second source ofunprogrammed position control signals is manually movable.

11. The control circuit of claim 9 in which said feedback signalgenerator is a resolver and said second source of unprogrammed positioncontrol signals is a differential resolver in series connection withsaid resolver.

12. The control system of claim 11 in which said differential resolveris electrically connected in a feedback loop between said resolver andsaid comparator.

13. The control system of claim 11 in which said differential resolvercomprises a stator and a rotor, said rotor being mechanically connectedto a manually rotatable position control dial.

14. The control system of claim 1 1 in which said variable speed motoris connected to a manually setable speed-control setting means.

15. The control system of claim 11 in which said variable speed motor isconnected through a closed servo loop with a manually setable speedcontrol setting means.

16. The control system of claim 15 in which said closed servo loopincludes a tachometer mechanically connected to said variable speedmotor,'a source of command speed control signals, and a comparator forgenerating an error signal representative of the difference between thecommand speed control signal and the actual speed of said variable speedmotor as measured at said tachometer.

17. A manual control system for a numerically controlled machine tool,which machine toolhas a movable slide, a motor for effecting movement ofsaid slide, a servo system including a feedback loop for controllingsaid motor, and a numerical control unit for supplying command inputinformation to said servo system, said manual control system comprisinga differential resolver located in the position feedback loop of theservo control system, and

a manually settable variable speed motor for driving said differentialresolver at a controlled rate so as to effect controlled feedingmovement of said slide independently of the numerical control unit.

18. The manual control system of claim 17 in which said differentialresolver is connected to a manually movable position control dial foreffecting manual positioning of said slide.

19, The controlsystem of claim17 in which said differential resolvercomprisesa stator and a rotor, said rotor being mechanically connectedto a manually rotatable position control dial.

20. The control system of claim 17 in which said variable speed'rnotor'is connected to a manually setable speed control setting means.

21. The control system of claim 17 in which said variable speed motor isconnected through a closed servo loop with a manually setable speedcontrol setting means.

22. The control system of claim 21 in which said closed servo loopincludes a tachometer mechanically connected to said variable speedmotor, a source of command speed control signals, and a comparator forgenerating an error signal representative of the difference between thecommand speed control signal and the actual speed of said variable speedmotor as measured at said tachometer.

23. A manual control system for a numerically controlled machine tool,which machine tool has movable slides, motors for effecting movement ofsaid slides, servo systems including feedback loops for controlling saidmotors, and a numerical control unit for supplying command inputinformation to said servo systems, said manual control system comprisingdifferential resolvers located in the position feedback loops of theservo control systems, and

manually settable variable speed motors for driving said differentialresolvers at controlled rates so as to effect controlled feedingmovement of said slides independently of the numerical control unit. 24.For use in combination with a numerically programmable machine having aslide and a motor for effecting movementof said slide, a control systemfor controlling energization of said motor, said control systemcomprising I a first source of programmable position and velocitycommand signals,

a comparator, I means for supplying a programmed command signal fromsaid first source of command signals to said comparator, means forsupplying an error signal from said parator to said motor, a feedbacksignal generator, means for supplying a feedback signal from saidfeedback signal generator to said comparator such that said error signalis representative of the difference between said command signal and saidfeedback signal, manually controllable position means for generatingposition control signals without the use of program format information,said manually controllable position means including a graduated dial forinput of manual position commands and for reading out slide positionwhen said slide is under the control of said manually controllableposition means, means for supplying position control signals from saidmanually controllable means to said comparator, and manuallycontrollable velocity means for driving said motor at a controlledvelocity without the use of program format information, said manuallyconcomtrollable velocity means being 'operatively con 25. The controlsystem of claim' 24 in which said,

manually controllable position means includes a differential resolver.

26. The control system of claim 25 in which said differential resolveris electrically connected in a feedback loop between said resolver andsaid comparator.

27. The control system of claim 25 in which said differential resolvercomprises a stator and a rotor, said rotor being mechanically connectedto a manually rotatable position control dial.

28. A control system for a numerically controlled machine tool which hasa movable slide, said control system including a motor for effectingmovement of said slide, a servo system including a feedback loop forcontrolling said motor, a numerical control unit for supplying programformat command input information to said servo system and a manualcontrol system, said manual control system comprising manuallycontrollable position means for generating position control signalswithout the use of program format information, said manuallycontrollable means including a graduated dial for input of positioncommands and for reading out slide position when said slide is under thecontrol of said manu ally controllable velocity means.

1. For use in combination with a numerically programmable machine havinga slide and a motor for effecting movement of said slide, a controlsystem for controlling energization of said motor, said control systemcomprising a first source of programmable position and velocity commandsignals, a comparator, means for supplying a programmed command signalfrom said first source of command signals to said comparator, means forsupplying an error signal from said comparator to said motor, a feedbacksignal generator, means for supplying a feedback signal from saidfeedback signal generator to said comparator such that said error signalis representative of the difference between said command signal and saidfeedback signal, a second source of unprogrammed position controlsignals, means for supplying position control signals from said secondsource to said comparator, and the improvement which comprises variablespeed motor means for driving said second source of position controlsignals at a controlled rate so as to control the velocity of slidemovement when said slide is under the control of said second source ofunprogrammed position control signals.
 2. For use in combination with anumerically programmable machine having a slide and a motor foreffecting movement of said slide, a control system for controllingenergization of said motor, said control system comprising a firstsource of programmed position and velocity command signals, acomparator, means for supplying a command signal from a said firstsource of command signals to said comparator, means for supplying anerror signal from said comparator to said motor, a feedback signalgenerator, means for supplying a feedback signal from said feedbacksignal generator to said comparator such that said error signal isrepresentative of the difference between said command signal and saidfeedback signal, a second manually actuated source of unprogrammedposition control signals, means for supplying position control signalsfrom said second source to said comparator, and the improvement whichcomprises variable speed motor means for driving said second source ofunprogrammed position control signals at a controlled rate so as tocontrol the velocity of slide movement when said slide is under thecontrol of said second source of position control signals.
 3. For use incombination with a numerically programmable machine having a slide and amotor for effecting movement of said slide, a control system forcontrolling energization of said motor, said control system comprising afirst source of programmed position command signals, a comparator, meansfor supplying a command signal from a said first source of commandsignals to said comparator, means for supplying an error signal fromsaid comparator to said motor, a resolver for generating a feedbacksignal, means for supplying said feedback signal from said resolver tosaid comparator such that said error signal is representative of thedifference between said command signal and said feedback signal, amanually setable differential resolver for generating unprogrammedcontrol signals, means for supplying said unprogrammed control signalsfrom said differential resolver to said comparator, and the improvementwhich comprises variable speed motor means for driving said differentialresolver at a controlled rate so as to control the velocity of slidemovement when said slide is under the control of unprogrammed controlsignals.
 4. The control system of claim 3 in which said differentialresolver is electrically connected in a feedback loop between saidresolver and said comparator.
 5. The control system of claim 3 in whichsaid differential resolver comprises a stator and a rotor, said rotorbeing mechanically connected to a manually rotatable position controldial.
 6. The control system of claim 3 in which said variable speedmotor is connected to a manually setable speed control setting means. 7.The control system of claim 3 in which said variable speed motor isconnected through a closed servo loop with a manually setable speedcontrol setting means.
 8. The control system of claim 7 in which saidclosed servo loop includes a tachometer mechanically connected to saidvariable speed motor, a source of command speed control signals, and acomparator for generating an error signal representative of thedifference between the command speed control signal and the actual speedof said variable speed motor as measured at said tachometer.
 9. For usein combination with a numerically controlled machine tool having a pairof slides movable along mutually perpendicular axes and a pair ofindependently operable motors for effecting movement of said slides, anumerical control system for controlling energization of said motors,said control system comprising a first source of programmable positionand velocity command signals for each of said motors, a pair ofcomparators, one of said comparators being in a control circuit for eachof said motors, means in each of said circuits for supplying aprogrammed command signal from said first source of command signals toeach of said comparators, means in each of said circuits for supplyingan error signal from said comparator to the motor controlled by saidcircuit, a feedback signal generator in each of said control circuits,means in each of said circuits for supplying a feedback signal from saidfeedback signal generator to said comparator such that said error signalis representative of the difference between said command signal and saidfeedback signal, a second source of unprogrammed position controlsignals in each of said circuits, means in each of said circuits forsupplying position control signals from said second source to thecomparator in said circuit, and the improvement which comprises variablespeed motor means in each of said circuits for driving said secondsource of position control signals at a controlled rate so as to controlthe velocity of slide movement when that slide is under the control ofsaid second source of unprogrammed position control signals.
 10. Thecontrol circuit of claim 9 in which said second source of unprogrammedposition control signals is manually movable.
 11. The control circuit ofclaim 9 in which said feedback signal generator is a resolver and saidsecond source of unprogrammed position control signals is a differentialresolver in series connection with said resolver.
 12. The control systemof claim 11 in which said differential resolver is electricallyconnected in a feedback loop between said resolver and said comparator.13. The control system of claim 11 in which said differential resolvercomprises a stator and a rotor, said rotor being mechanically connectedto a manually rotatable position control dial.
 14. The control system ofclaim 11 in which said variable speed motor is connected to a manuallysetable speed control setting means.
 15. The control system of claim 11in which said variable speed motor is connected through a closed servoloop with a manually setable speed control setting means.
 16. Thecontrol system of claim 15 in which said closed servo loop includes atachometer mechanically connected to said variable speed motor, a sourceof command speed control signals, and a comparator for generating anerror signal representative of the difference between the command speedcontrol signal and the actual speed of said variable speed motor asmeasured at said tachometer.
 17. A manual control system for anumerically controlled machine tool, which machine tool has a movableslide, a motor for effecting movement of said slide, a servo systemincluding a feedback loop for controlling said motor, and a numericalcontrol unit for supplying command input information to said servosystem, said manual control system comprising a differential resolverlocated in the position feedback loop of the servo control system, and amanually settable variable speed motor for driving said differentialresolver at a controlled rate so as to effect controlled feedingmovement of said slide independently of the numerical control unit. 18.The manual control system of claim 17 in which said differentialresolver is connected to a manually movable position control dial foreffecting manual positioning of said slide.
 19. The control system ofclaim 17 in which said differential resolver comprises a stator and arotor, said rotor being mechanically connected to a manually rotatableposition control dial.
 20. The control system of claim 17 in which saidvariable speed motor is connected to a manually setable speed controlsetting means.
 21. The control system of claim 17 in which said variablespeed motor is connected through a closed servo loop with a manuallysetable speed control setting means.
 22. The control system of claim 21in which said closed servo loop includes a tachometer mechanicallyconnected to said variable speed motor, a source of command speedcoNtrol signals, and a comparator for generating an error signalrepresentative of the difference between the command speed controlsignal and the actual speed of said variable speed motor as measured atsaid tachometer.
 23. A manual control system for a numericallycontrolled machine tool, which machine tool has movable slides, motorsfor effecting movement of said slides, servo systems including feedbackloops for controlling said motors, and a numerical control unit forsupplying command input information to said servo systems, said manualcontrol system comprising differential resolvers located in the positionfeedback loops of the servo control systems, and manually settablevariable speed motors for driving said differential resolvers atcontrolled rates so as to effect controlled feeding movement of saidslides independently of the numerical control unit.
 24. For use incombination with a numerically programmable machine having a slide and amotor for effecting movement of said slide, a control system forcontrolling energization of said motor, said control system comprising afirst source of programmable position and velocity command signals, acomparator, means for supplying a programmed command signal from saidfirst source of command signals to said comparator, means for supplyingan error signal from said comparator to said motor, a feedback signalgenerator, means for supplying a feedback signal from said feedbacksignal generator to said comparator such that said error signal isrepresentative of the difference between said command signal and saidfeedback signal, manually controllable position means for generatingposition control signals without the use of program format information,said manually controllable position means including a graduated dial forinput of manual position commands and for reading out slide positionwhen said slide is under the control of said manually controllableposition means, means for supplying position control signals from saidmanually controllable means to said comparator, and manuallycontrollable velocity means for driving said motor at a controlledvelocity without the use of program format information, said manuallycontrollable velocity means being operatively connected to saidgraduated dial of said manually controllable position means so that saidgraduated dial remains synchronized with slide movement when said slideis under the control of said manually controllable velocity means. 25.The control system of claim 24 in which said manually controllableposition means includes a differential resolver.
 26. The control systemof claim 25 in which said differential resolver is electricallyconnected in a feedback loop between said resolver and said comparator.27. The control system of claim 25 in which said differential resolvercomprises a stator and a rotor, said rotor being mechanically connectedto a manually rotatable position control dial.
 28. A control system fora numerically controlled machine tool which has a movable slide, saidcontrol system including a motor for effecting movement of said slide, aservo system including a feedback loop for controlling said motor, anumerical control unit for supplying program format command inputinformation to said servo system and a manual control system, saidmanual control system comprising manually controllable position meansfor generating position control signals without the use of programformat information, said manually controllable means including agraduated dial for input of position commands and for reading out slideposition when said slide is under the control of said manuallycontrollable position means, means for supplying position controlsignals from said manually controllable means to said servo system, andmanually controllable velocity means for driving said motor at acontrolled velocity without the use of program format information, saidmanually controllable Velocity means being operatively connected to saidgraduated dial so that said graduated dial remains synchronized withslide movement when said slide is under the control of said manuallycontrollable velocity means.